In order to trap PM (a particulate material) such as black smoke or SOF, exhausted from an internal combustion engine such as diesel engine or the like, a diesel particulate filter is used, and accompanying with the use thereof, a problem is raised that PM is deposited inside the filter, resulting in increase in pressure loss.
Accordingly, as countermeasure for PM deposition, the filter is conventionally regenerated by arranging a heating apparatus such as an electric heater at the filter, to combust and remove PM by heating (JP-B-2953409).
However, such a regeneration method had a problem of increased consumption power and high running cost. In addition, there was also a problem that space occupied by the heater apparatus, other than the filter, was required, which limited installment place in arrangement thereof in a vehicle. In order to solve these problems, a purification apparatus for diesel exhaust gas has been proposed, which comprises a filter for trapping diesel engine particulates, a catalyst converter having good activity to hydrocarbon (HC) installed at the upstream side of an exhaust gas pipeline of the filter, and an HC control unit enabling supplying a large quantity of HC to the catalyst converter, and as this catalyst, platinum, palladium or the like has been disclosed (JP-A-60-043113).
In addition, a filter for diesel exhaust gas particles, where a catalytic component is coated on the filter, has also been disclosed. However, this method has a problem of limited temperature range enabling regeneration, due to continuous increase in exhaustion pressure up to about 370° C., although not requiring fuel addition for filter regeneration (U.S. Pat. No. 5,100,632).
Still more, in a purification system of exhaust gas from an internal combustion engine, provided with a continuous regeneration-type diesel particulate filter at the exhaust gas passage of an internal combustion engine, for removing a particulate material trapped by regeneration mode operation, when trapped amount of a particulate material in the filter for trapping a particulate material becomes a predetermined judgment value or higher, there has also been proposed a purification system of exhaust gas from an internal combustion engine, which comprises a trapped amount estimation means for estimating trapped amount of a particulate material trapped at the above filter, and a maximal injection amount control means for limiting maximal injection amount of an internal combustion engine, when a particulate material estimated by the trapping amount estimation means becomes predetermined judgment value or higher (JP-A-2004-108207).
In addition, it has been known that, in a method for removing nitrogen oxides, catalytic performance is lowered caused by storage of sulfur oxides such as SOx to a NOx storage catalyst used in removal of NOx, and a regeneration method has been proposed, where a large quantity of hydrocarbon is introduced for temperature increase also in recovering the performance. However, this method limits temperature range suitable to regeneration (JP-B-3747693).